1. Field of the Invention
The present invention relates generally to electrical connectors, and particularly to a connector having internal circuitry capable of providing a specified electrical interface between various types of data handling equipment.
2. Description of the Prior Art
The proliferation of digital data processing equipment, first in business and now into the home, has created an ongoing demand for such equipment with ever increased capabilities but at an affordable price. The modern trend to integrate numerous discrete electrical components within single semiconductor integrated circuits or "chips", has provided for greater economies in the manufacture of digital electronic equipment. Not only is the overall physical size and weight of the equipment reduced through use of integrated circuit technology, but manufacturing costs also are alleviated in that the price of each integrated circuit used is but a fraction of the total cost represented by all the components it contains.
Digital data processing systems which are in common use today include portions arranged to allow the user to communicate with the system by way of, for example, a terminal or a printer. The user "talks" or provides information to the system through the terminal, and this information is converted into digital data which the system is capable of understanding. After the data is processed by the system which may include some form of computer, a suitable response is transmitted back to the user in digital form and then properly converted into visibly recognizable words or symbols on the screen of the terminal or on a sheet generated by a printer.
Accordingly, it is often necessary to provide cable interconnections between differently located units of a data processing system to allow the units to transmit and receive digital data to and from one another.
Certain types of digital equipment, e.g. a terminal or a printer, transmit or receive digital data in serial bit format. That is, each character (i.e., letter or numeral) of the data is sent or received one bit at a time. It will be appreciated that in a typical system where each character occupies multiple bits, communicating the characters as serial bits between separately located pieces of equipment reduces significantly the number of separate conductors which must be provided in the connecting cables, allows for the communicating equipments to operate in time synchronism with one another with regard to the data exchanged between them, as well as for the use of parity bits and other common error detecting techniques to be applied for each data character communicated. Other kinds of equipment in data handling systems operate in a parallel bit format. For example, computers operate on data which is loaded in internal registers one full character (i.e., eight bits) at a time, and likewise provide output information a character at a time to internal output registers.
In order to insure compatability between terminals, printers and other input/output data handling equipment which operate in a serial bit format, and computer mainframes and related equipment, the Electronic Industries Association promulgated in 1969 a now widely accepted interface standard known as EIA RS-232-C, the provisions of which are incorporated by reference herein. The RS-232-C Standard, entitled "Interface Between Data Terminal Equipment and Data Communication Equipment Employing Serial Binary Data Interchange", ensures that serial bit format equipment produced by one manufacturer will operate properly with serial bit format equipment of another manufacturer. The RS-232-C Standard applies not only to the interchange of information data signals between data handling equipment, but also to the interchange of timing and control data signals between such equipment (Sec. 1.4 of the Standard).
In order to ensure satisfactory noise immunity of the data signals to be communicated over connecting cables, the RS-232-C Standard provides that the data signals transmitted over the cables have magnitudes of at least .+-.6 volts (See Sec. 2.3 of the Standard). Since most data handling equipment today operate at five-volt levels, the Standard makes necessary additional power supplies for enabling a voltage level conversion of the data signals to be interchanged over the connecting cable.
With regard to mechanical characteristics of the interface, the RS-232-C Standard states that the interface is "located at a pluggable connector signal interface point between the two equipments. The female connector . . . should be mounted in a fixed position near the data terminal equipment". (Sec. 3.1). FIG. 3.1 within the RS-232-C Standard assigns certain circuit functions to each of 25 connector pins associated with the pluggable connector at the signal interface point. While the Standard does not specify a particular type of multiple pin connector (See Appendix I to the Standard), the "D-type" 25 pin connector (for example, AMP type 206584-1) has essentially become an industry standard.
A printed circuit board together with circuit components and software necessary to achieve an RS-232-C interface between a computer terminal on one side, and modems or serial line printers on the other side, is available from a variety of manufacturers. Such boards are mountable inside the computer, and separate cable is provided. These boards are compatible from the RS-232-C side but they differ on the computer side from computer to computer.
The known RS-232-C interfaces which include a printed circuit board are arranged physically as shown in FIG. 1. The board B can be a "stand alone card" and be connected via a card cage connector (not shown) to various parallel signal bus lines associated with a microprocessor in a computer or other terminal equipment (also not shown). Alternatively, it can be a part of a more complex board. The RS-232-C Standard 25-pin connector CON may be mounted along one edge of the board B as shown, and the pins directly connected electrically to printed conductors on the board by soldering as at points S on the underside of the board B. This leaves a female connector part F fixedly mounted near the data terminal equipment as required by the Standard. The various conductors to which the pins of the connector CON are connected lead to electrical circuitry arranged over other portions of the board B, including, for example, a main logic element chip IC 1, line driver IC 3, line receiver IC 4, crystal oscillator OSC, frequency divider IC 2, and a number of discrete components C.
It will be appreciated that the known RS-232-C interface board arrangements require that a certain amount of space be allocated in existing equipment for their insertion, such space often being at a premium in units intended to be portable and of small overall dimensions. As far as is known, there has been no attempt to integrate any electrical interface circuitry, including those components required to implement the RS-232-C interface as shown in FIG. 1, within the prescribed interface connector itself such as the 25-pin connector CON.
A connector is known from U.S. Pat. No. 3,790,858 to Brancaleone et al within which RF filter elements are connected to a number of parallel pin-like contact elements which are supported inside and extend axially through a cylindrical shell. The filter elements are connected internally between the contact elements and a common cylindrical metal ground plate.